Performance improvement of a wing with a controlled spanwise bending wingtip

Abstract

This paper aims to investigate the unsteady force characteristics and performance improvement of a wing with a controlled morphing wingtip. Taking the geometry nonlinearity of morphing into consideration, a new predictor-corrector method is developed to get the updated coordinates of nodes on the morphing wing surface. The effects of morphing frequency and amplitude are investigated. The results indicate that the unsteady force amplitude increases with the morphing frequency and amplitude. Meanwhile, the morphing amplitude affects the phase and harmonic characteristics of the force. The wingtip morphing influence on the unsteady force is divided into the shape effect and the additional angle of attack effect. The force can be described by a simple scaling law using a generalized Duffing-van-der-Pol nonlinear model. This scaling law depicts the nonlinear effect of large amplitude bending in essence. Afterward, the in-depth wake structures analysis of the flow field finds that the morphing frequency does not affect the essential feature of wake topology, while the morphing amplitude does. As the morphing amplitude increases, the vortical structures shift from vortical tubes to ring-like vortices, which induces the change of the phase and harmonic characteristic of force response.